1. Field of the Invention
The present invention relates generally to improvements in ignition timing control devices for internal combustion engines and more particularly to an ignition timing control device which is capable of varying the spark timing for a motor vehicle internal combustion engine so as to reduce the quantity of noxious gases exhausted from the engine in response to the temperature of the coolant within the engine water jacket without causing auxiliary engine complications such as for example the lowering of engine output power, a reduction in vehicle acceleration, or overheating of the engine.
2. Description of the Prior Art
It is a common practice to retard the spark timing of a motor vehicle internal combustion engine in order to reduce the quantity of noxious fumes which are discharged by the engine into the atmosphere and which is of course becoming so substantial as to present public health problems due to such air pollution. One conventional spark timing arrangement however which retards the spark timing of the engine uniformly, regardless of engine conditions, causes a substantial reduction in the output power of the engine, a lack of vehicle acceleration, and overheating of the engine, such conditions being particularly acute when the engine operates either at low temperature or under overheating conditions, the rotation of the engine components becoming unstable and the quality of the gases exhausted from the engine becoming still worse.